In need of a quick clamp I made 10 of these in 1/4 of an hour.
Since that I have found all sorts of uses for them.
A couple of saw cuts in some scrap wood I had around quickly produced the basic shape.
Although you could make them as large or small as you need my example is 10 mm square and 100 mm long or about 3/8 square and 4 inches long.
Wrap an elastic band round 2 of the parts and you have an instant clamp.
Move the band nearer the item to be clamped and increase the clamping strength.
Move it back to produce a milder pressure for delicate tasks.